This invention pertains to imaging apparatus and methods and more particularly, to apparatus and methods for cooling a sheet of media in an imaging apparatus.
Various types of prior art imaging apparatus have been in use. By xe2x80x9cimaging apparatusxe2x80x9d we mean an apparatus that is configured to produce a given image on a sheet of media. Imaging apparatus include such devices known as printers, copiers, fax machines, and plotters. By xe2x80x9cimagexe2x80x9d we mean to include any image, such as photographs, drawings, symbols, text, or any combination thereof, which is formed by depositing at least one shade or color of pigment onto a sheet of media. By xe2x80x9cmediaxe2x80x9d we mean any material onto which pigment can be affixed so as to form an image, including paper and plastic transparencies. That is, an image can range from simple black text on a white sheet of paper media to a complex color photograph on a transparency.
It is understood, then, that many different specific configurations of imaging apparatus exist. One such configuration of an imaging apparatus is that which is generally known as a laser printer. Referring now to FIG. 1, a schematic side elevation diagram is shown which depicts some of the basic components of a prior art laser printer apparatus 10. The prior art laser printer apparatus 10 comprises an infeed tray 22 and an outfeed tray 24. The infeed and outfeed trays 22, 24 are each configured to support at least one sheet of media xe2x80x9cM.xe2x80x9d
The prior art laser printer apparatus 10 also comprises a set of infeed rollers 14 which are configured to feed a given sheet of media xe2x80x9cMxe2x80x9d along a media path xe2x80x9cPxe2x80x9d in the feed direction xe2x80x9cD.xe2x80x9d As is seen, the prior art apparatus comprises an image-producing portion 12 which, in turn, generally comprises at least one laser device and one photoconductor surface (not shown). The image-producing portion 12 is configured to apply toner (not shown), which is in a substantially powdered form, to a sheet of media xe2x80x9cMxe2x80x9d in order to form an image thereon, while the sheet of media passes by the image-producing portion along the media path xe2x80x9cP.xe2x80x9d Laser printers are known in the art and, therefore the process of forming an image on a sheet of media by employing a laser device and photoconductor will not be discussed in further detail herein.
As is further evident from a study of FIG. 1, the prior art apparatus 10 comprises a fusing portion 16. The fusing portion 16 is configured to heat the media xe2x80x9cM,xe2x80x9d along with the toner supported thereon, to a given temperature in order to set, or xe2x80x9cfuse,xe2x80x9d the toner to the media. That is, generally the powdered toner, which is supported on a sheet of media xe2x80x9cM,xe2x80x9d is heated by the fusing portion 16 so that the toner is xe2x80x9cmeltedxe2x80x9d from its initial powdered form to a substantially xe2x80x9cplasticxe2x80x9d consistency. This fusing process in which the toner is substantially melted causes the toner to be substantially bonded to the media so as to form the final product of an image bonded to a sheet of media. During this fusing process, the temperature of the media xe2x80x9cMxe2x80x9d can reach significant levels and can be at least as high as 190xc2x0, Centigrade.
As is also seen, a set of outfeed rollers 18 is included in the prior art apparatus 10. The outfeed rollers 18 move the media xe2x80x9cM,xe2x80x9d after it has passed the fuser 16, into the outfeed tray 24. The media xe2x80x9cMxe2x80x9d which is supported in the outfeed tray 24 is generally accessible to users of the apparatus 10 so that the sheets of media xe2x80x9cM,xe2x80x9d which now support finished images, can be retrieved by the users of the apparatus 10. The location of the fusing portion 16 is generally fixed relative to the set of outfeed rollers 18. That is, a given fixed distance xe2x80x9cLxe2x80x9d is defined along the media path xe2x80x9cPxe2x80x9d between the fusing portion 16 and the set of outfeed rollers 18.
It is evident, then, that a given period of time which elapses between the moment at which a given sheet of media xe2x80x9cMxe2x80x9d passes through the fusing portion 16 and the moment at which the given sheet of media xe2x80x9cMxe2x80x9d passes through the set of outfeed rollers 18 is inversely proportional to the feed rate of the media along the feed path xe2x80x9cP.xe2x80x9dIn other words, faster feed rates, or production rates, will result in shorter elapsed times from the moment the media xe2x80x9cMxe2x80x9d passes through the fusing portion 16 and the moment at which the media is available for retrieval by the users of the apparatus 10.
Moving now to FIG. 2, a flow chart 30 is shown which depicts a set of prior art steps which can be used to describe the typical operational processes performed on a given sheet of media by the prior art laser printer apparatus 10 during the production of a finished image. The various steps of which the flow chart 30 is comprised will now be discussed with reference to both FIGS. 1 and 2. As is evident, the step S32 serves as the beginning of the flow chart 30. Moving on from step S32, the first operational step is that of S34. In accordance with step S34, a sheet of media xe2x80x9cMxe2x80x9d is taken from the infeed tray 22 and fed into the infeed rollers 14 so as to commence the movement of the media along the media path xe2x80x9cPxe2x80x9d and in the feed direction xe2x80x9cD.xe2x80x9d
Moving to the next step, that of S36, the sheet of media xe2x80x9cMxe2x80x9d is fed past the image-producing portion 12, and an image comprising toner is deposited on the media by the image-producing portion. In accordance with the following step S38, the sheet of media xe2x80x9cMxe2x80x9d is fed past the fusing portion 16, and the toner and media is heated by the fusing portion to a relatively high temperature in order to fuse the image to the media. The next step of S40 includes passing the sheet of media xe2x80x9cMxe2x80x9d through the outfeed rollers 18, and depositing the media in the outfeed tray 24. The step S42 denotes the end of the flow chart 30. As discussed above, the production rate of the prior art apparatus 10 is limited by the need to provide ample time for the media xe2x80x9cMxe2x80x9d to cool after passing through the fusing portion 16 and before passing through the outfeed rollers 18 and into the outfeed tray 24.
Briefly referring again to FIG. 1, it is evident that at relatively high feed rates, the media xe2x80x9cMxe2x80x9d has correspondingly less time to cool before exiting the apparatus 10 through the set of outfeed rollers 18. This can result in the exposure of users of the apparatus 10 to media xe2x80x9cMxe2x80x9d which is at dangerously high temperatures, which can cause severe burns. In addition, stacked sheets of media xe2x80x9cMxe2x80x9d which accumulate in the outfeed tray can contain high levels of heat energy which can cause damage to the media and to the apparatus 10, and can also pose a potential fire hazard.
Furthermore, when a media such as plastic transparencies are used in the apparatus 10, the cumulative heat energy which is present in a stack of such transparencies can cause one sheet of media to fuse to another sheet. Therefore, feed rates of prior art imaging apparatus, such as the prior art laser printer apparatus 10, are often limited by the need to allow the media xe2x80x9cMxe2x80x9d to cool sufficiently before being made available in the outfeed tray 24.
What is needed then, are imaging apparatus and methods which achieve the benefits to be derived from similar prior art devices, but which avoid the shortcomings and detriments individually associated therewith.
The invention includes apparatus and methods for cooling a sheet of media on which an image is deposited in an imaging process. Typically, such imaging processes involve heating the media to a relatively high temperature for fusing the image to the media. The instant invention includes various embodiments thereof which are configured to actively reduce the temperature of the media before the media exits the imaging apparatus.
In accordance with a first embodiment of the present invention, an imaging apparatus comprises a cooling surface which is configured to contact a sheet of media and to thereby absorb heat energy there from. The cooling surface can be configured to act as a heat sink to absorb spikes of heat energy from a succession of sheets of media. The heat energy thereby absorbed from the sheets of media can then be passively dissipated from the cooling surface to the surrounding atmosphere by natural convection, for example. The heat energy can also be actively dissipated from the cooling surface using various devices which are configured to facilitate such heat dissipation. The cooling surface can be substantially flat, substantially cylindrical, or can have other shapes.
In accordance with a second embodiment of the present invention, an imaging apparatus includes a cooling device, a cooling surface defined on the cooling device, and a fan assembly configured to induce a stream of air to flow relative to the cooling device. The air can be made to flow substantially across the media and can also be made to flow substantially across the cooling surface. The cooling device can be in the form of a substantially cylindrical roller. The cylindrical roller can be substantially hollow so as to define a cavity there in which allows air to circulate through the roller to facilitate cooling thereof.
In accordance with a third embodiment of the present invention, a method of cooling a sheet of media includes providing a cooling surface, contacting the sheet of media to the cooling surface, and transferring heat energy from the sheet of media to the cooling surface. The method can also include dissipating the heat energy from the cooling surface to the atmosphere.